You are checking each possible solution to determine whether or not it is a solution of the given equation (5x-1)^2 = 7. Note that you must follow order of operations rules. If you wish to check the possible root sqrt(7)/5 - 1,
subst. that into (5x-1)^2 = 7 and ask yourself whether the result is true or not.
(5 [ sqrt(7)/5 - 1 ] - 1 )^2 = 7 (true or false?)
( sqrt(7) - 5 - 1)^2 = 7 => (sqrt(7)-6)^2 = 7
7 - 12sqrt(7) + 36 = 7 is FALSE.
